This is a tough time for you Simonfromharlow, and I'm sorry for what you and the children are going through.
This may sound harsh, but I wonder if thinking about the hard practicalities of the separation would help you even a little bit? Like another PP I've found planning can help me get some form of control and help me think clearly.
Eg: Giving your mind tasks such as: what are your finances? Do you work outside the home or a SAHP? What access do you have to money - eg joint account? Do you, personally, have savings? What are the joint savings? What about the mortgage? Will you need to sell and each but somewhere smaller? You don't have to respond here - these are questions for you to consider for the next phase.
If you have not yet taken your own legal advice talk to your parents or Women's Aid for help and guidance.
You will need your own solicitor to help with the separation/divorce and a financial settlement.
He is still here until Tuesday but has been pretty absent.
Before he leaves and, I assume, takes all his documentation with him, gather and copy/photograph from your phone all relevant financial information when he's out, eg copies of his payslips, bank statements, pension statements for when you see your solicitor. Change the pin/passwords on your phone and other devices so he's unable to access correspondence about this situation.
Email the copied documents to a new email address you create which he is unable to access.
Do not tell him you are talking to a solicitor until you absolutely have to.
I'm sure you don't want to do any of this and maybe he'll be very fair but it will help you to focus on some of these practical issues a) to help keep yourself together and b) to ensure, when it comes to it, that you get the best financial deal for you and your children.
It will also help you have all this information if the split becomes less amicable from his side than it is now.
It hurts so much that he's so happy with himself now. Getting on with his life while I feel like this.
No I didn't see it coming at all.
He's had time (which you have not had) to think about and plan this. He is being practical about his next steps - you need to be too.
All this is easy for me to say and hard for you to do, so I'm wishing you strength for the future OP. 🌹